The Effect of Green Tea on Blood Pressure

The major risk factor for stroke and cardiovascular disease is hypertension.

In a cross-sectional study of 1507 Chinese subjects, the role of regular green tea consumption was investigated.

After
adjustment for confounding factors, including BMI, lifestyle and diet,
it was observed that daily consumption of 120–599ml of green tea per day
for at least one year reduced the risk of developing hypertension by
46%, compared to those subjects consuming less than 120 ml per day.

Consuming more than 600 ml per day reduced the risk by 65%.

These
results provide one possible explanation for the reduced mortality from
cardiovascular disease associated with regular green tea consumption.

For example, Mikhail A. Bokucha,
at the Bakh Institute of Biochemistry in Moscow, reported that tea in
Russian patients had been shown to relieve high blood pressure,
headaches, prevent thrombosis and strengthen blood vessels.

He called tea catechins "superior to every known capillary-strengthening drug".

Sedative Action

California investigators in 1984 reported that decaffeinated green tea had a sedative action in mice.

According
to James P. Henry, M.D., a professor of psychiatry at Loma Linda
University School of Medicine, the tea, stripped of its caffeine, seemed
to relax the animals by affecting the central nervous and
neuroendocrine system.

French
scientists have found the same thing in rats eating two specific
flavonoid compounds; their blood pressure dropped significantly.

The French concluded that the bioflavonoids probably lower blood pressure by performing like beta blocker drugs.

Other related studies have indicated that the rare amino acid called, L-theanine
(found in abundance in Japanese green tea), while effecting the
chemical state of the brain, also positively effects the peripheral
nervous system, diminishing hypertension and contribute to normalizing
blood pressure.

The amazing thing is that even green tea with caffeine has the same calming and relaxing effect.

The
L-theanine present in green tea seems to counterbalance the effect of
caffeine. This amino acid actually acts antagonistically against the
stimulatory effects of caffeine on the nervous system.

Research on human volunteers has demonstrated that L-theanine creates
a sense of relaxation in approximately 30-40 minutes after ingestion
via at least two different mechanisms.

First, this amino acid
directly stimulates the production of alpha brain waves, creating a
state of deep relaxation and mental alertness similar to what is
achieved through meditation.

Second, L-theanine is involved in the formation of the inhibitory neurotransmitter, gamma amino butyric acid (GABA).

GABA influences the levels of two other neurotransmitters, dopamine and serotonin, producing the key relaxation effect.

What Are ACE Inhibitors?

Another type of drugs used for heart disease are ACE inhibitors.

As
it turns out, green tea has more ACE-inhibiting compounds than any
other herb that can be used for heart disease (as well as at least 10
beta-blockers, 7 calcium channel blockers and 16 diuretics).

One
of the reasons for high blood pressure can be put down to overproduction
of an enzyme (angiotensin converting enzyme or ACE) which causes
angiotensin I to be converted into angiotensin II.

Angiotensin II is a hormone which causes constriction of blood vessels and an increase in blood pressure.

ACE
inhibitors, as the word suggests, inhibit this conversion allowing the
blood vessels to dilate causing a decrease in blood pressure.

Dr
Y. Hara, from the Japan Society for Bioscience and Biotechnology, has
shown that green tea catechin impedes the action of ACE and suppresses
production of angiotensin II.

He has also demonstrated that the
administration of catechin to mice with Spontaneously Hypertensive Rate
(SHR) can reduce high blood pressure.

Results of his experiments
indicate that daily consumption of green tea catechins have the ability
to prevent a rise in blood pressure.

These studies demonstrate the wonderful effect of green tea on blood
pressure and that consuming a moderate amount of green tea, on a regular
daily basis, can reduce blood pressure levels,
improving overall heath.